Mito-nuclear discordance with evidence of shared ancestral polymorphism and selection in cactophilic species ofDrosophila

Abstract

The Drosophila serido haplogroup is a monophyletic group composed of the following four cryptic and cactophilic species that are endemic to eastern Brazil: D. borborema, D. gouveai, D. seriema and D. serido. Here, we investigate the mito‐nuclear discordance in these species found among the cytochrome c oxidase subunit I (COI) mitochondrial gene, the autosomal alpha‐Esterase‐5 (α‐Est5) and the X‐linked period gene (per). Our analysis indicates that shared polymorphisms in these three molecular markers may be explained by the maintenance of ancestral polymorphisms rather than introgressive hybridization. The primary structures of COI, per and α‐Est5 genes evolve primarily under purifying selection, but we detected some sites that evolved under positive selection in α‐Est5. Considering the high variability of cacti species in eastern Brazil and the role attributed to Drosophila esterases in digestion metabolism and/or the detoxification of several compounds found in cactus tissues, we conjecture about the role of natural selection triggered by host shifts as an important factor in the intraspecific diversification of the D. serido haplogroup.

Lineage diversity and gene introgression in freshwater cladoceran crustaceans of the Chydorus sphaericus species complex

“…Indeed, hybridization is especially common in zooplankton (Hebert 1985), especially in the genus Daphnia (Ma et al 2019 a ). However, other explanations for cyto‐nuclear discordances, for instance incomplete lineage sorting of ancestral polymorphisms (Franco et al 2015), or selection acting on mitochondrial genes (Pavlova et al 2013), cannot be ruled out. Further work, such as the use of high‐resolution nuclear markers (such as microsatellites) or relevant experimental crossings, will be required to confirm hybridization in the C. sphaericus species complex.…”

Divergent clades or cryptic species? Mito-nuclear discordance in a Daphnia species complex

“…Incomplete lineage sorting (ILS) of ancestral polymorphisms is another possible scenario [ 17 , 19 ] as assumed for example for the mito-nuclear discordance observed in the Drosophila serido haplogroup [ 21 ]. Distinguishing between ILS and introgression is difficult and often the only indications might be drawn from genetic data.…”

“…On the one hand, nuclear mitochondrial pseudogenes (numts) or pseudogenes from the mitochondrial genome that originate from duplication events might be amplified rather than the functional target gene [ 18 ]. On the other hand, cyto-nuclear discordance may be caused by various biological processes, like hybridization and subsequent introgression of the mitochondrial genome [ 15 , 16 , 19 ], incomplete lineage sorting of ancestral polymorphisms [ 19 – 21 ], or selection acting on mitochondrial genes, either direct due to, e.g., environmental factors [ 22 , 23 ], or through indirect selection induced by maternally inherited symbionts [reviewed by 24 ]. Thus, firm conclusions about the delimitations of species based on genetic data should be drawn from a combination of different approaches, e.g., combining mtDNA and nuclear DNA, and assessing evidence on the level of gene flow between putative species.…”

Consequences of the last glacial maximum onNyctelia confusa(Coleoptera: Tenebrionidae) in Patagonia

“…Mardulyn, Mikhailov & Pasteels () proposed that a zone of secondary contact may homogenize the genetic diversity in Chrysomelidae, making it equal to the diversity of the rest of the populations. Moreover, the absence of genetic structure in mitochondrial (mt)DNA in insects could be a consequence of the maintenance of ancestral polymorphism or even the occurrence of introgressive mtDNA hybridization (Franco et al ., ), although this must be evaluated further to obtain more evidence.…”